How To Use Local Functions In C# 7.0

What are Local Functions in C# 7.0?

The local function is an ability to declare methods inside an already defined function’s body. We are able to write local functions in C# 6.0 too but they can’t have a complete body or function name, and can only be anonymous.

Why Local Functions in C# 7.0?

As per the Microsoft blog, this is already (kind of) possible by using the Func and Action types with anonymous methods.

However, they lack a few features,

Generics
ref and out parameters
params

How to write Local Functions in C# 7.0

Local functions have the same capabilities as normal methods but will only be scoped to the block they were declared in.

Now, let’s try to write a normal local function first.

In the following image of code, you can check that I just created a function with two argument types (int, string) and it has all the behavior as a normal function. Since it is a local function, you can use or call it within the same function only.

Code

static void Main(string[] args)
{
string myFunc(int p1,string p2)
{
return p2.Substring(p1);
}
Console.WriteLine(myFunc(2,"Nitin Pandit"));
Console.Read();
}

We can also use other properties of local function, like Generics, ref/out parameters, and params. So, let’s see how to use them.

Local Generics Functions
Local Generic function is really a nice property. It can be used in the same way as in a normal function and we can call it within the root function. In the following example, I have created myFunc as Generic.

Code
1. static void Main(string[] args)
2. {
3. void myFunc<T>(T value)
4. {
5. Console.WriteLine(value);
6. }
9. myFunc<string>("Nitin Pandit");
10. Console.Read();
11. }
Using out/ref in Local Functions

Code
1. static void Main(string[] args)
2. {
3. void myFunc(int value1, out int value2)
4. {
5. value2 = value1 + value1;
6. Console.WriteLine();
7. }
8. int i = 0;
9. myFunc(12, out i);
10. Console.WriteLine($"New Value of i : {i}");
11. Console.Read();
12. }
Using params in Local Functions

Code
1. static void Main(string[] args)
2. {
3. void myFunc(params int[] items)
4. {
5. int res = 0;
6. foreach (var item in items)
7. {
8. res += item;
9. }
10. Console.WriteLine($"Total : {res}");
11. }
13. myFunc(1,2,3,4,5,6,7,8,9);
15. Console.Read();
16. }

All these properties of local function make C# 7.0 more powerful. Thanks for reading this article. Stay tuned with us for more updates:

Connect (“Nitin Pandit”);